Tetrafullerene conjugates for all-organic photovoltaics

G. Fernández, L. Sánchez, D. Veldman, M.M. Wienk, C.M. Atienza, D.M. Guldi, R.A.J. Janssen, N. Martin

Research output: Contribution to journalArticleAcademicpeer-review

40 Citations (Scopus)

Abstract

The synthesis of two new tetrafullerene nanoconjugates in which four C60 units are covalently connected through different -conjugated oligomers (oligo(p-phenylene ethynylene) and oligo(p-phenylene vinylene)) is described. The photovoltaic (PV) response of these C60-based conjugates was evaluated by using them as the only active material in organic solar cells, showing a low PV performance. Photophysical studies in solution demonstrated a very fast (~10 ps) deactivation of the singlet excited state of the central core unit to produce both charge-separated species (i.e., C60--oligomer+-(C60)3 and C60 centered singlet excited states). The charge-separated state recombines partly to the C60 centered singlet state that undergoes subsequent intersystem crossing. Photophysical studies carried out in films support these data, exhibiting long-lived triplet excited states. For both tetrafullerene arrays, the low yield of long-lived charge carriers in thin films accounts for the limited PV response. On the contrary, utilizing the oligo(p-phenylene vinylene) centered precursor aldehyde as an electron donor and antennae unit and mixing with the well-known C60 derivative PCBM, the photophysical studies in films show the formation of long-lived charges. The PV devices constructed from these mixtures showed a relatively high photocurrent of 2 mA cm-2. The sharp contrast between the nanoconjugates and the physical blends tentatively was attributed to improved charge dissociation and the collection of more favorable energy levels in the blends as a result of partial aggregation of both of the components.
Original languageEnglish
Pages (from-to)3189-3196
Number of pages8
JournalJournal of Organic Chemistry
Volume73
Issue number8
DOIs
Publication statusPublished - 2008

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